RowNumberer and Grouping feature showing extra group column header

RowNumberer and Grouping feature showing extra group column header

Ext JS version - 4.1.3

When using a RowNumberer column in a Grid with Grouping feature, the group header is being shown twice. Once for the grouped data, as expected, but also over the rowNumberer column. In addition, the header over the rowNumberer column is using the same groupHeaderTpl as grouped data, effectively showing the group header twice in the same row.

This appears to be a bug, or at least a feature to me. It does violate my principle of least surprise when using the rowNumberer with Grouping. Is this a bug?

I would expect the normal group header to span the whole row, and the rowNumberer header to not be present in the group header. Or, at the very least, the rowNumberer group header to be blank and not duplicate the same groupHeaderTpl as the grouped data.

If you need a code example, I can generate one. I can't share the actual code.